Organic insulating composition.



UNITED STATES PATENT OFFICE.

mo H. nnnxnnann, or yonxnns, NEW YORK, Assmiiba'ro GENERAL naknnm courm, or. NEW YORK, n. 1., A conrona'rron or mzwxoax.

Specification of Letters Patent.

llo Drawing. Original application llled December 4, 1907, Serial No. 405,022. Divided and this application filed December 81, 1914.

To all whom it may concern Be it known thatl, LEO H. BAEKELAND,

a citizen of the United States, residing at dure', without injury, a far of overload than is the case w ere fusible or Yonkers, in the county of Westchester and State of New York, have invented certam new and useful Improvements in Organic Insulating Composition, of which the following is a specification.

- "The object of-this invention is to provide an organic insulating composition which is more particularly adapted for coil-lmpregnating purposes by reason its capability k of being transformed, under the influence of heat, from a mobile and penetrative liquid into a homggeneous, impervious and highlyinsulatingsolid. ,This transformation takes place without. any considerable amount of evaporation or change of volume, owing to formed in situ into an-insulating solid of the character described, this solid serving both to insulate and to su port coil-wind-- ings'. Owing to the infus1b1lity of the supporting mass, such coils are enabled to en:

resinous products are used; and owing to v the insolub'ility of the mass, it may be directly immersed in oil, and may be used under conditions involvm exposure to water or. steam, to acid or' a kaline liquids, or to organic or inorganic solvents, without infur, WhlCh is well known to exert a strong I Or a' full understanding of my invention I willdescribe a preferred method of preparing the composltion.

' Phenol. or its homologues isimixed with formaldehyde in approximately equal molecular proportions, preferably-with the addition of small proportions of catalytic or condensing agents, and the mixture is heated,,preferably in a vessel provided with a return condenser. After some time,dependingupon the temperature and the propo tion of condensing agents used, the mixtn' separates into two layers, the one aqueous and the other oily or viscous; the latter resents the first reaction products andfis" hereinafter referred toas the,initial1con;- densation product. 'This initial -.con'dens'ation product is soluble :inalcohol, acetone,

eater degree Serial No. 879,946.

phenol and other solvents, but is only imperfectly and partially soluble in benzoL- If 'sufliciently cooled it may become pasty Patented Jan. 23, 1917.

or stifl", and sometimes brittle, but is readily liquefied by application of heat, and in it's fluid-and mobile condition possessesexcellent penetrative powers, and readily penetrates not only the coil-interstices, but also,

the fibrous coating of the coils,if such be.

uSed.- If subjected to sufficiently prolon ed heating under proper conditions it is fina 1y transformedtinto a hard condensation prod-- not, which is insoluble in alcohol, acetone, phenol, or glycerin, and remains solid at temperatures below 300 0.; at higher temperatures it does not fuse, although some carbomzation may occur. This material is a .solid, homogeneous, impervious, infusible,

and insoluble body which possesses excellent insulat ng properties and is hereinafter referred to as the final condensation prod uct., This final condensation product presents many advantages as compared with hard rubber, and other insulators as heretofore used. In particular, it may be mentioned' that it is capable of withstandin temperatures at which hard rubber woul be entirely destroyed, so that coils impregnated therewith can withstanda very heavy overload without= injury. 'Furthermore, it does not fuse at any temperature, althou h as above stated, carbonization may ta e place when it is excessively heated. It possesses the important advantage, as compared.

with hard rubber, that it is free from sulcorrosive action upon copper, articularly at and it is advisable to expel these by heat before transforming it .into the final condensation product. Such heating should preferably be effected under reduced pressure and at low temperatures in order to void premature conversion with. loss of obility. :The liquid condensation pro'duct 'g' s lthen applied'to the coil in'such manner as completelyto impregnate the same, the impregnation .being assisted, f necessary,

- this purpose. In this and in all other cases pregnation, the initial condensation product may be used alone or in admixture with other substances such as asbestos, insulating fillings and the like; or it may be applied in mixture With materials adapted to facilitate the coating or the subsequent hardening op,- eration or to insure proper flexibility of the final coating. If desired the conductors may be previously coated with cotton, silk, asbestos, insulating varnishes or the like, which are then coated or impregnated with the v initial condensation product. The coated conductor, coil or other construction I is'then' subjected to a hardening operation to transform the initial condensation product into a final infusibleand insoluble condensation product having the properties above described. Although in the case of thin insulating layers this may be accomplished by simple" heating, especially if the temperatures do not exceed 100 (3., this is a slow and very uncertain process. In order to hasten the transformation but more especially so as to obtain a pro-duct of-maximum, hardness and best qualities it is desirable to apply heat at temperatures considerably above 100 Q, and in this case the hardening operation should be conducted under increased pressure; for otherwise the heating may expel volatile constituents or liberate gaseous decomposition products throughout the body of the material and in-such an'irregular way as to destroy its homogeneity, rendering it porous or cellular in character,

and greatly impairing its value as an insulator. In certain cases as when the coil or other construction is closed or is covered by an external layer or envelop, or casing, the internal pressure developed by the volatile constituents liberated under the action of heat, may be suflicient to prevent foaming and to insure homogeneous hardening, but it is usually desirable or necessary to maintain during the heating or hardening process, an appropriate external pressure,

as for instance by conducting the hardening operation-1n hermetically closed chambers, or

envelops,;heat being applied in any suitable manner and the temperature being maintained preferably between 120 and 200 C. The pressure may be applied by means of compressed air or by a compressed inert gas in the latter case superficial oxidation of the coating is avoided. .As an alternative method the coating may be hardened while immersed in an inert liquid maintained under pressure; the liquid hydrocarbons or mineral oils being particularly suited for the hardening may be conveniently effected by passing through'the previously coated conductor an electric current suflicient to heat the coating to the desired temperature and for a suiiicient period of time. This. hardening may be regarded, from a chemical point of view, as an effect due to the polymerization of the initial condensation product, the material acquiring by and during the act of polymerization the qualities of infusibility and insolubility.

I am aware that it has been proposed to employ for insulating purposes a plastic body made by boiling together phenol and formaldehyde with forty to eighty per cent. of sulfuric acid having a concentration of 16 to 17 B., and I do not claim such product, which is entirely inapplicable to the impregnation of coils. In the first place, a product thus prepared persistently retains free acid, which. would render it inapplicable densing agents as described is not merely to accelerate the reaction, but also to insure that practically all of the phenol or its homologues shall enter into reaction with the formaldehyde. In the absence of suchcon- (lensing agents a large proportion of the phenolic body and the formaldehyde remains uncombined at the time the fluid or mobile stage is reached, and the subsequent hardening is effected by a process of slow evaporation, involving the elimination of volatile materials, a decided shrinkage in volume, and the consequent distortion of the product. I

The term phenol is to be understood as including the homologues of phenol, such as cresol, and the term formaldehyde is to be understood as including the polymers and, equivalents of formaldehyde.

This application is a division of my copending application Serial No. 405,022, filed .December 4, 1907.

impervious, and infusible solid of high insulating value.

2. An organic insulating composition adapted for coil-impregnation, said composition containing a phenolic condensation product and being initially fluid and mobile, but transformable by heat without substantial change of volume into a homogeneous, impervious, and infusible solid of high insulating value and substantially free from" adapted for coil-impregnation, said composition containing a phenolic condensation productand a material imparting flexibili v tot-he final product, the composition being initially fluid and mobile but transformable by heat without substantial change of volume'into a homogeneous, impervious, and

infusible solid of-high. insulating value and substantially free from volatile constituents,

sulfur, and acid-reacting substances.

In testimony whereof I afiix my signature an presence of two witnesses.

LEO H. BAEKELAND.

Witnesses:

HYm'ox SEVAN, HERBERT S. MA!- 

